Cisco IOS based networking devices provide several features that can be used to implement basic security for CLI sessions using only the operating system running on the device. These features include the following:

•Different levels of authorization for CLI sessions to control access to commands that can modify the status of the networking device versus commands that are used to monitor the device

•Assigning passwords to CLI sessions

•Requiring users log in to a networking device with a username

•Changing the privilege levels of commands to create new authorization levels for CLI sessions.

This module is a guide to implementing a baseline level of security for your networking devices. It focuses on the least complex options available for implementing a baseline level of security. If you have networking devices installed in your network with no security options configured, or you are about to install a networking device and you need help understanding the how to implement a baseline of security, this document will help you.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.

Your networking device must not be configured to use any local or remote authentication, authorization, and accounting (AAA) security features. This document describes only the non-AAA security features that can be configured locally on the networking device.

Benefits of Creating a Security Scheme for Your Networking Device

The foundation of a good security scheme in the network is the protection of the user interfaces of the networking devices from unauthorized access. Protecting access to the user interfaces on your networking devices prevents unauthorized users from making configuration changes that can disrupt the stability of your network or compromise your network security.

The Cisco IOS XE features described in this document can be combined in many different ways to create a unique security scheme for each of your networking devices. Here are some possible examples that you can configure:

•You can enable non administrative users to run a subset of the administrative commands available on the networking device by lowering the entitlement level for the commands to the non administrative privilege level. This can be useful for the following scenarios:

Cisco IOS XE CLI Modes

To aid in the configuration of Cisco devices, the Cisco IOS XE command-line interface is divided into different command modes. Each command mode has its own set of commands available for the configuration, maintenance, and monitoring of router and network operations. The commands available to you at any given time depend on the mode you are in. Entering a question mark(?) at the system prompt (router prompt) allows you to obtain a list of commands available for each command mode.

The use of specific commands allows you to navigate from one command mode to another. The standard order in which a user would access the modes is as follows: user EXEC mode; privileged EXEC mode; global configuration mode; specific configuration modes; configuration submodes; and configuration subsubmodes.

Note The default configuration of a Cisco IOS XE software based networking device only allows you to configure passwords to protect access to user EXEC mode (for local, and remote CLI sessions) and privileged EXEC mode. This document describes how you can provide additional levels of security by protecting access to other modes, and commands, using a combination of usernames, passwords and the privilege command.

Most EXEC mode commands are one-time commands, such as show or more commands, which show the current configuration status, and clear commands, which clear counters or interfaces. EXEC mode commands are not saved across reboots of the router.

From privileged EXEC mode, you can enter global configuration mode. In this mode, you can enter commands that configure general system characteristics. You also can use global configuration mode to enter specific configuration modes. Configuration modes, including global configuration mode, allow you to make changes to the running configuration. If you later save the configuration, these commands are stored across router reboots.

From global configuration mode you can enter a variety of protocol-specific or feature-specific configuration modes. The CLI hierarchy requires that you enter these specific configuration modes only through global configuration mode. For example, interface configuration mode, is a commonly used configuration mode.

From configuration modes, you can enter configuration submodes. Configuration submodes are used for the configuration of specific features within the scope of a given configuration mode. As an example, this chapter describes the subinterface configuration mode, a submode of the interface configuration mode.

ROM monitor mode is a separate mode used when the router cannot boot properly. If your system (router, switch, or access server) does not find a valid system image to load when it is booting, the system will enter ROM monitor mode. ROM monitor (ROMMON) mode can also be accessed by interrupting the boot sequence during startup. ROMMON is not covered in this document because it does not have any security features available in it.

The following sections contain detailed information on these command modes:

User EXEC Mode

When you start a session on a router, you generally begin in user EXEC mode, which is one of two access levels of the EXEC mode. For security purposes, only a limited subset of EXEC commands are available in user EXEC mode. This level of access is reserved for tasks that do not change the configuration of the router, such as determining the router status.

If your device is configured to require users to log-in the log-in process will require a username and a password. You may try three times to enter a password before the connection attempt is refused.

User EXEC mode is set by default to privilege level 1. Privileged EXEC mode is set by default to privilege level 15. For more information see the "Privileged EXEC Mode" section. When you are logged into a networking device in user EXEC mode your session is running at privilege level 1. By default the EXEC commands at privilege level 1 are a subset of those available at privilege level 15. When you are logged into a networking device in privileged EXEC mode your session is running at privilege level 15. You can move commands to any privilege level between 1 and 15 using the privilege command. See the "Cisco IOS XE Privilege Levels" section for more information on privilege levels and the privilege command.

In general, the user EXEC commands allow you to connect to remote devices, change terminal line settings on a temporary basis, perform basic tests, and list system information.

To list the available user EXEC commands, use the following command:

Command

Purpose

Router(config)# ?

Lists the user EXEC mode commands

The user EXEC mode prompt consists of the host name of the device followed by an angle bracket (>), as shown in the following example:

Router>

The default host name is generally Router, unless it has been changed during initial configuration using the setup EXEC command. You also change the host name using the hostname global configurationcommand.

Note Examples in Cisco IOS XE documentation assume the use of the default name of "Router." Different devices (for example, access servers) may use a different default name. If the routing device (router, access server, or switch) has been named with the hostname command, that name will appear as the prompt instead of the default name.

To list the commands available in user EXEC mode, enter a question mark (?) as shown in the following example:

Router> ?

Exec commands:

<1-99> Session number to resume

connect Open a terminal connection

disconnect Disconnect an existing telnet session

enable Turn on privileged commands

exit Exit from Exec mode

help Description of the interactive help system

lat Open a lat connection

lock Lock the terminal

login Log in as a particular user

logout Exit from Exec mode and log out

menu Start a menu-based user interface

mbranch Trace multicast route for branch of tree

mrbranch Trace reverse multicast route to branch of tree

mtrace Trace multicast route to group

name-connection Name an existing telnet connection

pad Open a X.29 PAD connection

ping Send echo messages

resume Resume an active telnet connection

show Show running system information

systat Display information about terminal lines

telnet Open a telnet connection

terminal Set terminal line parameters

tn3270 Open a tn3270 connection

trace Trace route to destination

where List active telnet connections

x3 Set X.3 parameters on PAD

The list of commands will vary depending on the software feature set and router platform you are using.

Note You can enter commands in uppercase, lowercase, or mixed case. Only passwords are case sensitive. However, Cisco IOS XE documentation convention is to always present commands in lowercase.

Privileged EXEC Mode

In order to have access to all commands, you must enter privileged EXEC mode, which is the second level of access for the EXEC mode. Normally, you must enter a password to enter privileged EXEC mode. In privileged EXEC mode, you can enter any EXEC command, because privileged EXEC mode is a superset of the user EXEC mode commands.

Because many privileged EXEC mode commands set operating parameters, privileged EXEC level access should be password protected to prevent unauthorized use. The privileged EXEC command set includes those commands contained in user EXEC mode. Privileged EXEC mode also provides access to configuration modes through the configure command, and includes advanced testing commands, such as debug.

Privileged EXEC mode is set by default to privilege level 15. User EXEC mode is set by default to privilege level 1. For more information see the "User EXEC Mode" section. When you are logged into a networking device in privileged EXEC mode your session is running at privilege level 15. When you are logged into a networking device in user EXEC mode your session is running at privilege level 1. By default the EXEC commands at privilege level 15 are a superset of those available at privilege level 1. You can move commands to any privilege level between 1 and 15 using the privilege command. See the "Cisco IOS XE Privilege Levels" section for more information on privilege levels and the privilege command.

The privileged EXEC mode prompt consists of the host name of the device followed by a pound sign(#), as shown in the following example:

Router#

To access privileged EXEC mode, use the following command:

Command

Purpose

Router> enable

Password

Router# exit

Router>

Enables privileged EXEC mode.

•If a privileged EXEC mode password has been configured the system will prompt you for a password after you issue the enable command.

•Use the exit command to leave privileged EXEC mode.

Note Privileged EXEC mode is sometimes referred to as "enable mode," because the enable command is used to enter the mode.

If a password has been configured on the system, you will be prompted to enter it before being allowed access to privileged EXEC mode. The password is not displayed on the screen and is case sensitive. If an enable password has not been set, privileged EXEC mode can be accessed only by a local CLI session (terminal connected to the console port).

If you attempt to access privileged EXEC mode on a router over a remote connection, such as a telnet connection, and you have not configured a password for privileged EXEC mode you will see the % No password set error message. For more information on remote connections see the "Remote CLI Sessions" section. The system administrator uses the enable secret or enable password global configuration commands to set the password that restricts access to privileged EXEC mode. For information on configuring a password for privileged EXEC mode, see the "Protecting Access to Privileged EXEC Mode" section.

To return to user EXEC mode, use the following command:

Command

Purpose

Router# disable

Exits from privileged EXEC mode to user EXEC mode.

The following example shows the process of accessing privileged EXEC mode:

Router> enable

Password:<letmein>

Router#

Note that the password will not be displayed as you type, but is shown here for illustrational purposes.To list the commands available in privileged EXEC mode, issue the ? command at the prompt. From privileged EXEC mode you can access global configuration mode, which is described in the following section.

Note Because the privileged EXEC command set contains all of the commands available in user EXEC mode, some commands can be entered in either mode. In Cisco IOS XE documentation, commands that can be entered in either user EXEC mode or privileged EXEC mode are referred to as EXEC mode commands. If user or privileged is not specified in the documentation, assume that you can enter the referenced commands in either mode.

Global Configuration Mode

The term "global" is used to indicate characteristics or features that affect the system as a whole. Global configuration mode is used to configure your system globally, or to enter specific configuration modes to configure specific elements such as interfaces or protocols. Use the configure terminal privileged EXEC command to enter global configuration mode.

To access global configuration mode, use the following command in privileged EXEC mode:

Command

Purpose

Router#configure terminal

From privileged EXEC mode, enters global configuration mode.

The following example shows the process of entering global configuration mode from privileged EXEC mode:

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#

Note that the system prompt changes to indicate that you are now in global configuration mode. The prompt for global configuration mode consists of the host-name of the device followed by (config) and the pound sign (#). To list the commands available in privileged EXEC mode, issue the ? command at the prompt.

Commands entered in global configuration mode update the running configuration file as soon as they are entered. In other words, changes to the configuration take effect each time you press the Enter or Return key at the end of a valid command. However, these changes are not saved into the startup configuration file until you issue the copy running-config startup-config EXEC mode command. This behavior is explained in more detail later in this document.

As shown in the example above, the system dialogue prompts you to end your configuration session (exit configuration mode) by pressing the Control (Ctrl) and "z" keys simultaneously; when you press these keys, ^Z is printed to the screen. You can actually end your configuration session by entering the Ctrl-Z key combination, using the end command, using the Ctrl-C key combination. The end command is the recommended way to indicate to the system that you are done with the current configuration session.

Caution If you use Ctrl-Z at the end of a command line in which a valid command has been typed, that command will be added to the running configuration file. In other words, using Ctrl-Z is equivalent to hitting the Enter (Carriage Return) key before exiting. For this reason, it is safer to end your configuration session using the
end command. Alternatively, you can use the Ctrl-C key combination to end your configuration session without sending a Carriage Return signal.

You can also use the exit command to return from global configuration mode to EXEC mode, but this only works in global configuration mode. Pressing Ctrl-Z or entering the end command will always take you back to EXEC mode regardless of which configuration mode or configuration submode you are in.

To exit global configuration command mode and return to privileged EXEC mode, use one of the following commands:

Command

Purpose

Router(config)# end

or

Router(config)# ^Z

Ends the current configuration session and returns to privileged EXEC mode.

Router(config)# exit

Exits the current command mode and returns to the preceding mode. For example, exits from global configuration mode to privileged EXEC mode.

From global configuration mode, you can enter a number of protocol-specific, platform-specific, and feature-specific configuration modes.

Interface configuration mode, described in the following section, is an example of a configuration mode you can enter from global configuration mode.

Interface Configuration Mode

One example of a specific configuration mode you enter from global configuration mode is interface configuration mode.

Many features are enabled on a per-interface basis. Interface configuration commands modify the operation of an interface such as an Ethernet, FDDI, or serial port. Interface configuration commands always follow an interface global configuration command, which defines the interface type.

For details on interface configuration commands that affect general interface parameters, such as bandwidth or clock rate, refer to the Release 12.2 Cisco IOS Interface Configuration Guide. For protocol-specific commands, refer to the appropriate Cisco IOS XE software command reference.

To access and list the interface configuration commands, use the following command:

Command

Purpose

Router(config)# interface type number

Specifies the interface to be configured, and enters interface configuration mode.

In the following example, the user enters interface configuration mode for serial interface 0. The new prompt, hostname(config-if)#, indicates interface configuration mode.

Configuration submodes are configuration modes entered from other configuration modes (besides global configuration mode). Configuration submodes are for the configuration of specific elements within the configuration mode. One example of a configuration submode is subinterface configuration mode, described in the following section.

Subinterface Configuration Mode

From interface configuration mode, you can enter subinterface configuration mode. Subinterface configuration mode is a submode of interface configuration mode. In subinterface configuration mode you can configure multiple virtual interfaces (called subinterfaces) on a single physical interface. Subinterfaces appear to be distinct physical interfaces to the various protocols.

For detailed information on how to configure subinterfaces, refer to the appropriate documentation module for a specific protocol in the Cisco IOS XE software documentation set.

To access subinterface configuration mode, use the following command in interface configuration mode:

Command

Purpose

Router(config-if)# interfacetypenumber

Specifies the virtual interface to be configured and enters subinterface configuration mode.

In the following example, a subinterface is configured for serial line 2, which is configured for Frame Relay encapsulation. The subinterface is identified as "2.1" to indicate that it is subinterface 1 of serial interface 2. The new prompt hostname(config-subif)# indicates subinterface configuration mode. The subinterface can be configured to support one or more Frame Relay PVCs.

Router(config)# interface serial 2

Router(config-if)# encapsulation frame-relay

Router(config-if)# interface serial 2.1

Router(config-subif)#

To exit subinterface configuration mode and return to interface configuration mode, use the exit command. To end your configuration session and return to privileged EXEC mode, press Ctrl-Z or enter the end command.

Cisco IOS XE CLI Sessions

Local CLI Sessions

Local CLI sessions require direct access to the the console port of the networking device. Local CLI sessions start in user EXEC mode. See the "Cisco IOS XE CLI Modes" section for more information on the different modes that are supported on your networking device. All of the tasks required to configure and manage a networking device can be done using a local CLI session. The most common method for establishing a local CLI session is to connect the serial port on a PC to the console port of the networking device and then to launch a terminal emulation application on the PC. The type of cable and connectors required and the settings for the terminal emulation application on the PC are dependant on the type of networking device that you are configuring. See to the documentation for your networking device for more information on setting it up for a local CLI session.

Remote CLI Sessions

Remote CLI sessions are created between a host such as a PC and a networking device such as a router over a network using a remote terminal access application such as Telnet and Secure Shell (SSH). Local CLI sessions start in user EXEC mode. See the "Cisco IOS XE CLI Modes" section for more information on the different modes that are supported on your networking device. Most of the tasks required to configure and manage a networking device can be done using a remote CLI session. The exceptions are tasks that interact directly with the console port (such as recovering from a corrupted operating system (OS) by uploading a new OS image over the console port) and interacting with the networking device when it is in ROM Monitor Mode.

This document explains how to configure security for remote Telnet sessions. Telnet is the most common method for accessing a remote CLI session on a networking device.

Note SSH is a more secure alternative to Telnet. SSH provides encryption for the session traffic between your local management device such as a PC and the networking device that you are managing. Encrypting the session traffic with SSH prevents hackers that might intercept the traffic from being able to decode it. See Secure Shell Version 2 Support feature module for more information on using SSH.

Terminal Lines are Used for Local and Remote CLI Sessions

Cisco networking devices use the word lines to refer to the software components that manage local and remote CLI sessions. You use the lineconsole0 global configuration command to enter line configuration mode to configure options, such as a password, for the console port.

Router# configure terminal

Router(config)# line console 0

Router(config-line)# passwordpassword-string

Remote CLI sessions use lines that are referred to virtual teletypewriter (VTY) lines. You use the linevtyline-number [ending-line-number]global configuration command to enter line configuration mode to configure options, such as a password, for remote CLI sessions.

Router# configure terminal

Router(config)# line vty 0 4

Router(config-line)# passwordpassword-string

Protect Access to Cisco IOS XE EXEC Modes

Cisco IOS XE provides the ability to configure passwords that protect access to the following:

Protecting Access to Privileged EXEC mode

The second step in creating a secure environment for your networking device is protecting access to privileged EXEC mode with a password. The method for protecting access to privileged EXEC mode is the same for local and remote CLI sessions.

You protect access to privileged EXEC mode by configuring a password for it. This is sometimes referred to as the enable password because the command to enter privileged EXEC mode is enable.

Command

Purpose

enable

Example:

Router> enable

Password

Router#

Enables privileged EXEC mode.

•Enter your password if prompted. The password will not be shown in the terminal window.

•The ">" at the end of the prompt string is changed to a "#" to indicate that you are in privileged EXEC mode.

Cisco IOS XE Password Encryption Levels

Some of the passwords that you configure on your networking device are saved in the configuration in plain text. This means that if you store a copy of the configuration file on a disk, anybody with access to the disk can discover the passwords by reading the configuration file. The following password types are stored as plain text in the configuration by default:

•Console passwords for local CLI sessions

•Virtual terminal line passwords for remote CLI sessions

•Username passwords using the default method for configuring the password

•Privileged EXEC mode password when it is configured with the enable passwordpassword command

•Authentication key chain passwords used by RIPv2 and EIGRP

•BGP passwords for authenticating BGP neighbors

•OSPF authentication keys for authenticating OSPF neighbors

•ISIS passwords for authenticating ISIS neighbors

This excerpt from a router configuration file shows examples of passwords and authentication keys that are stored as clear text.

!

enable password O9Jb6D

!

username username1 password 0 kV9sIj3

!

key chain trees

key 1

key-string willow

!

interface Ethernet1/0.1

ip address 172.16.6.1 255.255.255.0

ip router isis

ip rip authentication key-chain trees

ip authentication key-chain eigrp 1 trees

ip ospf authentication-key j7876

no snmp trap link-status

isis password u7865k

!

line vty 0 4

password V9jA5M

!

You can encrypt these clear text passwords in the configuration file by using the service password-encryption command. This should be considered only a minimal level of security because the encryption algorithm used by the service password-encryption command to encrypt passwords creates text strings that be decrypted using tools that are publicly available. You should still protect access to any electronic or paper copies of your configuration files after you use the service password-encryption command.

The service password-encryption command does not encrypt the passwords when they are sent to the remote device. Anybody with a network traffic analyzer who has access to you network can capture these passwords from the packets as they are transmitted between the devices. See the "Configuring Password Encryption for Clear Text Passwords" section for more information on encrypting clear text passwords in configuration files.

Many of the Cisco IOS XE features that use clear text passwords can also be configured to use the more secure MD5 algorithm. The MD5 algorithm creates a text string in the configuration file that is much more difficult to decrypt. The MD5 algorithm does not send the password to the remote device. This prevents people using a traffic analyzer to capture traffic on your network from being able to discover your passwords.

You can determine the type of password encryption that has been used by the number that is stored with the password string in the configuration file of the networking device. The number 5 in the configuration excerpt below indicates that the enable secret password has been encrypted using the MD5 algorithm.

!

enable secret 5 $1$fGCS$rkYbR6.Z8xo4qCl3vghWQ0

!

The number 7 in the excerpt below indicates that the enable password has been encrypted using the less secure algorithm used by the service password-encryption command.

!

enable password 7 00081204

!

Cisco IOS XE CLI Session Usernames

After you have protected access to user EXEC mode and privileged EXEC mode by configuring passwords for them you can further increase the level of security on your networking device by configuring usernames to limit access to CLI sessions to your networking device to specific users.

Usernames that are intended to be used for managing a networking device can be modified with additional options such as:

See the Cisco IOS Security Command Reference. (http://www.cisco.com/en/US/docs/ios/security/command/reference/sec_book.html) for more information on how to configure the username command.

Cisco IOS XE Privilege Levels

The default configuration for Cisco IOS XE based networking devices uses privilege level 1 for user EXEC mode and privilege level 15 for privileged EXEC. The commands that can be run in user EXEC mode at privilege level 1 are a subset of the commands that can be run in privileged EXEC mode at privilege 15.

The privilege command can also be used to assign a privilege level to a username so that when a user logs in with the username, the session will run at the privilege level specified by the privilege command. For example if you want your technical support staff to view the configuration on a networking device to help them troubleshoot network problems without being able to modify the configuration, you can create a username, configure it with privilege level 15, and configure it to run the show running-config command automatically. When a user logs in with the username the running configuration will be displayed automatically. The user's session will be logged out automatically after the user has viewed the last line of the configuration. See the "Configuring and Verifying a Networking Device to Allow Non Administrative Users to View the Running Configuration Automatically: Example" section for an example of how to configure this option.

These command privileges can also be implemented when using AAA with TACACS+ and RADIUS. For example, TACACS+ provides two ways to control the authorization of router commands on a per-user or per-group basis. The first way is to assign privilege levels to commands and have the router verify with the TACACS+ server whether or not the user is authorized at the specified privilege level. The second way is to explicitly specify in the TACACS+ server, on a per-user or per-group basis, the commands that are allowed. For more information about implementing AAA with TACACS+ and RADIUS, see the technical note How to Assign Privilege Levels with TACACS+ and RADIUS.

Cisco IOS XE Password Configuration

Cisco IOS XE software does not prompt you to repeat any passwords that you configure to verify that you have entered the passwords exactly as you intended. New passwords, and changes to existing passwords, go into effect immediately after you press the Enter key at the end of a password configuration command string. If you make a mistake when you enter a new password and have saved the configuration on the networking device to its startup configuration file and exited privileged EXEC mode before you realize that you made a mistake, you may find that you are no longer able to manage the device.

The following are common situations that can happen:

•You make a mistake configuring a password for local CLI sessions on the console port.

–If you have properly configured access to your networking device for remote CLI sessions, you can Telnet to it and reconfigure the password on the console port.

•You make a mistake configuring a password for remote Telnet or SSH sessions.

–If you have properly configured access to your networking device for local CLI sessions, you can connect a terminal to it and reconfigure the password for the remote CLI sessions.

•You make a mistake configuring your username password, and the networking device requires that you log into it with your username.

–If you do not have access to another account name, you will have to perform a lost password recovery procedure.

To protect yourself from having to perform a lost password recovery procedure open two CLI sessions to the networking device and keep one of them in privilege EXEC mode while you reset the passwords using the other session. You can use the same device (PC or terminal) to run the two CLI sessions or two different devices. You can use a local CLI session and a remote CLI session or two remote CLI sessions for this procedure. The CLI session that you use to configure the password can also be used to verify that the password was changed properly. The other CLI session that you keep in privileged EXEC mode can be used to change the password again if you made a mistake the first time you configured it.

You should not save password changes that you have made in the running configuration to the startup configuration until you have verified that your password was changed successfully. If you discover that you made a mistake configuring a password, and you were not able to correct the problem using the second CLI session technique described above, you can power cycle the networking device so that it returns to the previous passwords that are stored in the startup configuration.

Protecting Access to User Exec Mode

Configuring and Verifying a Password for Remote CLI Sessions

This task will assign a password for remote CLI sessions. After you have completed this task the networking device will prompt you for a password the next time that you start a remote CLI session with it.

Cisco IOS XE based networking devices require that you have a password configured for remote CLI sessions. If you attempt to start a remote CLI session with a device that doesn't have a password configured for remote CLI sessions you will see a message that a password is required and has not been set. The remote CLI session will be terminated by the remote host.

Prerequisites

If you have not previously configured a password for remote CLI sessions, you must perform this task over a local CLI session using a terminal or a PC running a terminal emulation application, attached to the console port.

Your terminal, or terminal emulation application, must be configured with the settings that are used by the console port on the networking device. The console ports on most Cisco networking devices require the following settings: 9600 baud, 8 data bits, 1 stop bit, no parity, and flow control is set to "none." See the documentation for your networking device if these settings do not work for your terminal.

To perform the verification step (Step 6) for this task, your networking device must have an interface that is in an operational state. The interface must have a valid IP address.

Restrictions

If you have not previously configured a password for remote CLI sessions, you must perform this task over a local CLI session using a terminal attached to the console port.

SUMMARY STEPS

1. enable

2. configureterminal

3. linevty line-number [ending-line-number]

4. passwordpassword

5. end

6. telnet ip-address

7. exit

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configureterminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

linevtyline-number[ending-line-number]

Example:

Router(config)# line vty 0 4

Enters line configuration mode.

Step 4

password password

Example:

Router(config-line)# password H7x3U8

The argument password is a character string that specifies the line password. The following rules apply to the password argument:

•The first character cannot be a number.

•The string can contain any alphanumeric characters, including spaces, up to 80 characters. You cannot specify the password in the format number-space-anything.

•Passwords are case sensitive.

Step 5

end

Example:

Router(config-line)# end

Exits the current configuration mode and returns to privileged EXEC mode.

Step 6

telnetip-address

Example:

Router# telnet 172.16.1.1

Start a remote CLI session with the networking device from your current CLI session using the IP address of an interface in the networking device that is in an operational state (interface up, line protocol up).

•Enter the password that you configured is step 4 when prompted.

Note This procedure is often referred to as a starting a recursive Telnet session because you are initiating a remote Telnet session with the networking device from the networking device itself.

Troubleshooting Tips

What to Do Next

Configuring and Verifying a Password for Local CLI Sessions

This task will assign a password for local CLI sessions over the console port. After you have completed this task, the networking device will prompt you for a password the next time that you start a local CLI session on the console port.

This task can be performed over a local CLI session using the console port or a remote CLI session. If you want to perform the optional step of verifying that you configured the password correctly you should perform this task using a local CLI session using the console port.

Prerequisites

If you want to perform the optional step of verifying the local CLI session password, you must perform this task using a local CLI session. You must have a terminal or a PC running a terminal emulation program, connected to the console port of the networking device. Your terminal must be configured with the settings that are used by the console port on the networking device. The console ports on most Cisco networking devices require the following settings: 9600 baud, 8 data bits, 1 stop bit, no parity, and flow control is set to "none." See the documentation for your networking device if these settings do not work for your terminal.

SUMMARY STEPS

1. enable

2. configureterminal

3. lineconsole0

4. passwordpassword

5. end

6. exit

7. Press the Enter key, and enter the password from Step 4 when prompted.

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configureterminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

line console 0

Example:

Router(config)# line console 0

Enters line configuration mode and selects the console port as the line that you are configuring.

Step 4

password password

Example:

Router(config-line)# passwordJi8F5Z

The argument password is a character string that specifies the line password. The following rules apply to the password argument:

•The first character cannot be a number.

•The string can contain any alphanumeric characters, including spaces, up to 80 characters. You cannot specify the password in the format number-space-anything.

•Passwords are case sensitive.

Step 5

end

Example:

Router(config-line)# end

Exits the current configuration mode and returns to privileged EXEC mode.

Step 6

exit

Example:

Router# exit

Exits privileged EXEC mode.

Step 7

Press the Enter key.

(Optional) Initiates the local CLI session on the console port.

•Enter the password that you configured is step 4 when prompted to verify that it was configured correctly.

Note This step can be performed only if you are using a local CLI session to perform this task.

Configuring and Verifying the Enable Password

Cisco no longer recommends that you use the enablepasswordcommand to configure a password for privileged EXEC mode. The password that you enter with the enablepassword command is stored as plain text in the configuration file of the networking device. You can encrypt the password for the enablepassword command in the configuration file of the networking device using the service password-encryption command. However the encryption level used by the service password-encryption command can be decrypted using tools available on the Internet.

Restrictions

The networking device must not have a password configured by the enable secret command in order to perform this task successfully. If you have already configured a password for privileged EXEC mode using the enable secret command, the password configured takes precedences over the password that you configure in this task using the enable password command.

You cannot use the same password for the enable secret command and the enablepassword command.

SUMMARY STEPS

1. enable

2. configureterminal

3. enable password password

4. end

5. exit

6. enable

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configureterminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

enable password password

Example:

Router(config)# enable password t6D77CdKq

The argument password is a character string that specifies the enable password. The following rules apply to the password argument:

•Can have leading spaces, but they are ignored. However, intermediate and trailing spaces are recognized.

•Can contain the question mark (?) character if you precede the question mark with the key combination Crtl-v when you create the password; for example, to create the password abc?123, do the following:

–Enter abc

–Type Crtl-v

–Enter ?123

Step 4

end

Example:

Router(config)# end

Exits the current configuration mode and returns to privileged EXEC mode.

What to Do Next

Configuring Password Encryption for Clear Text Passwords

Cisco IOS XE stores passwords in clear text in network device configuration files for several features such as passwords for local and remote CLI sessions, and passwords for neighbor authentication for routing protocols. Clear text passwords are a security risk because anybody with access to archived copies of the configuration files can discover the passwords that are stored as clear text. The service password-encryption command can be used to encrypt clear text commands in the configuration files of networking devices. See the "Cisco IOS XE Password Encryption Levels" section for more information.

Perform the following steps to configure password encryption for passwords that are stored as clear text in the configuration files of your networking device.

Prerequisites

You must have at least one feature that uses clear text passwords configured on your networking device for this command to have any immediate effect.

Exits the current configuration mode and returns to privileged EXEC mode.

Configuring and Verifying the Enable Secret Password

Cisco recommends that you use the enable secret command, instead of the enablepassword command to configure a password for privileged EXEC mode. The password created by the enable secret command is encrypted with the more secure MD5 algorithm.

Restrictions

You cannot use the same password for the enable secret command and the enablepassword command.

•Can have leading spaces, but they are ignored. However, intermediate and trailing spaces are recognized.

•Can contain the question mark (?) character if you precede the question mark with the key combination Crtl-v when you create the password; for example, to create the password abc?123, do the following:

–Enter abc

–Type Crtl-v

–Enter ?123

or

Sets a previously encrypted password for privileged EXEC mode by entering the number 5 before the previously encrypted string. You must enter an exact copy of a password from a configuration file that was previously encrypted by the enablesecret command to use this method.

Step 4

end

Example:

Router(config)# end

Exits the current configuration mode and returns to privileged EXEC mode.

The tasks in this section describe how to configure your networking device to permit the use of a subset of privileged EXEC mode commands by users who should not have access to all of of the commands available in privileged EXEC mode.

These tasks are beneficial for companies that have multiple levels of network support staff and the company wants the staff at each level to have access to a different subset of the privileged EXEC mode commands.

In this task the users who should not have access to all of of the commands available in privileged EXEC mode are referred to as the first-line technical support staff.

Configuring the Networking Device for the First-Line Technical Support Staff

This task describes how to configure the networking device for first-line technical support users. First-line technical support staff are usually not allowed to run all of the commands available in privileged EXEC mode (privilege level 15) on a networking device. They are prevented from running commands that they are not authorized for by not being granted access to the password assigned to privileged EXEC mode or to other roles that have been configured on the networking device.

The privilege command is used to move commands from one privilege level to another in order to create the additional levels of administration of a networking device that is required by companies that have different levels of network support staff with different skill levels.

The default configuration of a Cisco IOS XE device permits two types of users to access the CLI. The first type of user is a person who is only allowed to access user EXEC mode. The second type of user is a person who is allowed access to privileged EXEC mode. A user who is only allowed to access user EXEC mode is not allowed to view or change the configuration of the networking device, or to make any changes to the operational status of the networking device. On the other hand, a user who is allowed access to privileged EXEC mode can make any change to a networking device that is allowed by the CLI.

In this task the two commands that normally run at privilege level 15 are reset to privilege level 7 using the privilege command in order that first-line technical support users will be allowed to run the two commands. The two commands for which the privilege levels will be reset are the clearcounters command and reload command.

•The clearcounters command is used to reset the counter fields on interfaces for statistics such as packets received, packets transmitted, and errors. When a first-line technical support user is troubleshooting an interface related connectivity issue between networking devices, or with remote users connecting to the network, it is useful to reset the interface statistics to zero and them monitor the interfaces for a period of time to see if the values in the interface statistics counters change.

•The reload command is used initiate a reboot sequence for the networking device. One common use of the reload command by first-line technical support staff is to cause the networking device to reboot during a maintenance window so that it loads a new operating system that was previously copied onto the networking device's file system by a user with a higher level of authority.

Restrictions

You must not have the aaa new-model command enabled on the networking device. You must not have the loginlocal command configured for the local CLI sessions over the console port or the remote CLI sessions.

Note For clarity, only the arguments and keywords that are relevant for each step are shown in the syntax for the steps in this task. See the Cisco IOS command reference book for your Cisco IOS release for further information on the additional arguments and keywords that can be used with these commands.

Caution Do not use the no form of the
privilege command to reset the privilege level of a command to its default because it might not return the configuration to the correct default state. Use the
reset keyword for the
privilege command instead to return a command to its default privilege level. For example, to remove the
privilegeexec levelreload command from the configuration and return the
reload command to its default privilege of 15, use the
privilegeexec resetreload command
.

SUMMARY STEPS

1. enable password

2. configureterminal

3. enablesecretlevellevelpassword

4. privilegeexeclevellevelcommand-string

5. end

DETAILED STEPS

Step 1 enablepassword

Enters privileged EXEC mode. Enter the password when prompted.

Router> enable

Step 2 configureterminal

Enters global configuration mode.

Router# configureterminal

Step 3 enablesecretlevellevelpassword

Configures a new enable secret password for privilege level 7.

Router(config)# enablesecretlevel7Zy72sKj

Step 4 privilegeexeclevellevelcommand-string

Changes the privilege level of the clearcounters command from privilege level 15 to privilege level 7.

Router(config)# privilegeexeclevel7clearcounters

Step 5 end

Exits global configuration mode.

Router(config)# end

Verifying the Configuration for the First-Line Technical Support Staff

This task describes how to verify that the network device is configured correctly for the first-line technical support staff.

Prerequisites

The following commands must have been modified to run at privilege level 7 for this task:

•clearcounters

•reload

SUMMARY STEPS

1. enablelevel password

2. showprivilege

3. clearcounters

4. clearip route *

5. reloadin time

6. reloadcancel

7. disable

8. showprivilege

DETAILED STEPS

Step 1 enablelevelpassword

Logs the user into the networking device at the privilege level specified for the level argument.

Router> enable7Zy72sKj

Step 2 showprivilege

Displays the privilege level of the current CLI session

Router# showprivilege

Current privilege level is 7

Step 3 clearcounters

The clear counters command clears the interface counters. This command has been changed from privilege level 15 to privilege level 7.

Router# clearcounters

Clear "show interface" counters on all interfaces [confirm]

Router#

02:41:37: %CLEAR-5-COUNTERS: Clear counter on all interfaces by console

Step 4 cleariproute*

The ip route argument string for the clear command should not be allowed because it was not changed from privilege level 15 to privilege level 7.

Troubleshooting Tips

If your configuration does not work the way that you want it to and you want to remove the privilege commands from the configuration, use the reset keyword for the privilege command to return the commands to their default privilege level. For example, to remove the command privilegeexec levelreload command from the configuration and return the reload command to its default privilege of 15 use the privilegeexec resetreload command.

Configuring and Verifying the Networking Device to Require a Username for the First-Line Technical Support Staff

This task configures the networking device to require that the first-line technical support staff login to the networking device with a login name of admin. The admin username configured in this task is assigned the privilege level of 7 which will allow users who log in with this name to run the commands that were reassigned to privilege level 7 in the previous task. When a user successfully logs in with the admin username, the CLI session will automatically enter privilege level 7.

Enhanced Username Password Security

Before Cisco IOS XE Release 2.3, two types of passwords were associated with usernames: Type 0, which is a clear text password visible to any user who has access to privileged mode on the router, and type 7, which has a password encrypted by the service password encryption command.

In Cisco IOS XE Release 2.3 and later releases, the new secret keyword for the username command allows you to configure Message Digest 5 (MD5) encryption for username passwords.

Prerequisites

The following commands must have been modified to run at privilege level 7 for this task:

Restrictions

MD5 encryption for the username command is not supported in versions of Cisco IOS software prior to Cisco IOS XE Release 2.3.

You must not have the aaa-new model command enabled on the networking device. You must not have the loginlocal command configured for the local CLI sessions over the console port or the remote CLI sessions.

Note For clarity, only the arguments and keywords that are relevant for each step are shown in the syntax for the steps in this task. Refer to the Cisco IOS command reference book for your Cisco IOS XE release for further information on the additional arguments and keywords that can be used with these commands.

SUMMARY STEPS

1. enable password

2. configureterminal

3. usernameusernameprivilegelevelsecretpassword

4. end

5. disable

6. loginusernamepassword

7. show privilege

8. clearcounters

9. cleariproute*

10. reloadin 10

11. reloadcancel

12. disable

13. showprivilege

DETAILED STEPS

Step 1 enablet6D77CdKq

Enters privileged EXEC mode. Enter the password when prompted.

Router> enable

Step 2 configureterminal

Enters global configuration mode.

Router# configureterminal

Step 3 usernameusernameprivilegelevelsecretpassword

Creates a username and applies MD5 encryption to the password text string.

Router(config)# usernameadminprivilege7secretKd65xZa

Step 4 end

Exits global configuration mode.

Router(config)# end

Step 5 disable

Exits the current privilege level and returns to user EXEC mode.

Router# disable

Step 6 loginusername

Logs in the user. Enter the username and password you configured in step 3 when prompted.

Router> loginadmin

Step 7 show privilege

The show privilege command displays the privilege level of the CLI session.

Router# show privilege

Current privilege level is 7

Step 8 clearcounters

The clearcounters command clears the interface counters. This command has been changed from privilege level 15 to privilege level 7.

Router# clearcounters

Clear "show interface" counters on all interfaces [confirm]

Router#

02:41:37: %CLEAR-5-COUNTERS: Clear counter on all interfaces by console

Step 9 clearip route *

The ip route argument string for the clear command is not allowed because it was not changed from privilege level 15 to privilege level 7.

Recovering from a Lost or Misconfigured Password for Local CLI Sessions

There are three methods that can be used to recover from a lost or misconfigured password for local CLI sessions over console port. The method that you will use depends on the current configuration of your networking device.

Networking Device Is Configured to Allow Remote CLI Sessions

The fastest method to recover from a lost, or misconfigured password for local CLI sessions is to establish a remote CLI session with the networking device and repeat the "Configuring and Verifying a Password for Local CLI Sessions" section. Your networking device must be configured to allow remote CLI sessions and you must know the remote CLI session password to perform this procedure.

Networking Device Is Not Configured to Allow Remote CLI Sessions and the Local CLI Session Password Has Not Been Saved to the Startup Configuration File

If you cannot establish a remote session to your networking device, and you have not saved the misconfigured local CLI session password to the startup configuration, you can restart the networking device. When the networking device starts up again it will read the startup configuration file. The previous local CLI session password is restored.

Caution Restarting a networking device will cause it to stop forwarding traffic. This will also cause an interruption in any services that are running on the networking device, such as a DHCP server service, to stop. You should only restart a networking device during a period of time that has been allocated for network maintenance.

Networking Device Is Not Configured to Allow Remote CLI Sessions and the Local CLI Session Password Has Been Saved to the Startup Configuration File

If you can not establish a remote CLI session with the networking device, and you have saved the misconfigured local CLI session password to the startup configuration, or you have lost the local CLI session password, you must perform a password recovery procedure. Password recovery procedures are device specific. You must locate the document that describes the procedure for your type of networking device. See "Technical Assistance" sectionfor more Cisco Support information for your networking device.

Recovering from a Lost or Misconfigured Password for Remote CLI Sessions

There are three methods that can be used to recover from a lost, or misconfigured remote CLI session password. The method that you will use depends on the current configuration of your networking device.

Networking Device Is Configured to Allow Local CLI Sessions

The fastest method to recover from a lost, or misconfigured password for remote CLI sessions is to establish a local CLI session with the networking device and repeat the "Configuring and Verifying a Password for Remote CLI Sessions" section. Your networking device must be configured to allow local CLI sessions and you must know the local CLI session password to perform this procedure.

Networking Device Is Not Configured to Allow Local CLI Sessions and the Remote CLI Session Password Has Not Been Saved to the Startup Configuration File

If you cannot establish a local CLI session to your networking device, and you have not saved the misconfigured remote CLI session password to the startup configuration, you can restart the networking device. When the networking device starts up again it will read the startup configuration file. The previous remote CLI session password is restored.

Caution Restarting a networking device will cause it to stop forwarding traffic. This will also cause an interruption in any services that are running on the networking device, such as a DHCP server service, to stop. You should only restart a networking device during a period of time that has been allocated for network maintenance.

Networking Device Is Not Configured to Allow Local CLI Sessions and the Remote CLI Session Password Has Been Saved to the Startup Configuration File

If you can not establish a local CLI session with the networking device, and you have saved the misconfigured remote CLI session password to the startup configuration, or you have lost the remote CLI session password, you must perform a password recovery procedure. Password recovery procedures are device specific. You must locate the document that describes the procedure for your type of networking device. See "Technical Assistance" sectionfor more Cisco Support information for your networking device.

Recovering from a Lost or Misconfigured Passwords for Privileged EXEC Mode

There are two methods that can be used to recover from a lost, or misconfigured Privileged EXEC Mode password. The method that you will use depends on the current configuration of your networking device.

A Misconfigured Privileged EXEC Mode Password Has Not Been Saved to the Startup Configuration File

If you have not saved the misconfigured privileged EXEC mode password to the startup configuration, you can restart the networking device. When the networking device starts up again it will read the startup configuration file. The previous privileged EXEC mode password is restored.

Caution Restarting a networking device will cause it to stop forwarding traffic. This will also cause an interruption in any services that are running on the networking device, such as a DHCP server service, to stop. You should only restart a networking device during a period of time that has been allocated for network maintenance.

A Misconfigured Privileged EXEC Mode Password Has Been Saved to the Startup Configuration File, or the Privileged EXEC Mode Password Has Been Lost

If you have saved the misconfigured privileged EXEC mode password to the startup configuration, or you have lost the privileged EXEC mode password, you must perform a password recovery procedure. Password recovery procedures are device specific. You must locate the document that describes the procedure for your type of networking device. See "Technical Assistance" sectionfor more Cisco Support information for your networking device.

The following example shows how to configure the networking device to allow a non administrative users (no access to privileged EXEC mode) to view the running configuration automatically. This example requires that the username is configured for privilege level 15 because many of the commands in the configuration file can be viewed only by users who have access to privilege level 15.

The solution is to temporarily allow the user access to privilege level 15 while running the showrunning-config command and then terminating the CLI session when the end of the configuration file has been viewed. In this example the networking device will automatically terminate the CLI session when the end of the configuration file has been viewed. No further configuration steps are required.

Caution You must include the
noescape keyword for the
username command to prevent the user from entering an escape character that will terminate viewing the configuration file and leave the session running at privilege level 15.

The following section using the login command shows the user logging in to the networking device with the username of admin:

R1> login

Username: admin

Password:

The following section using the showprivilege command shows that the current privilege level is 7:

R1# show privilege

Current privilege level is 7

The following section using the showuser command shows that admin is the only user currently logged in to the networking device:

R1# show user

Line User Host(s) Idle Location

* 0 con 0 admin idle 00:00:00

Interface User Mode Idle Peer Address

The following section shows that the admin user is permitted to shutdown and enable an interface:

R1# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)# interface ethernet 1/0

R1(config-if)# shutdown

R1(config-if)# no shutdown

R1(config-if)# exit

R1#

Where to Go Next

Once you have established a baseline of security for your networking devices you can consider more advanced options such as:

•Role-Based CLI Access—The role-based CLI access feature offers a more comprehensive set of options than the privilege command (described in this document) for network managers who want to allow different levels of technical support staff to have different levels of access to CLI commands.

•AAA Security—Many Cisco networking devices offer an advanced level of security using authentication, authorization and accounting (AAA) features. All of the tasks described in this document, and other - more advanced security features - can be implemented using AAA on the networking device in conjunction with a remote TACACS+ or RADIUS server. For information how to configure AAA security features that can be run locally on a networking device, or for information on how to configure remote AAA security using TACACS+ or RADIUS servers, see the Cisco IOS XE Security Configuration Guide:Securing User Services, Release 2.

Additional References

The following sections provide references related to Configuring Security with Passwords and, Login Usernames for CLI Sessions on Networking Devices.

RFCs

No new or modified RFCs are supported by this functionality, and support for existing RFCs has not been modified.

—

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.

Note Table 2 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE software release train also support that feature.

All other trademarks mentioned in this document or website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0907R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.